Honestly, if I had to pick one then I think I might say Iroh. I mean, he's an amazing guy. His attitude, his philosophy, and his kindheartedness all made him a personal favorite of mine.

However, Toph is probably a close second - especially since I am visually impaired myself. I can still see, but am actually considered legally blind. So seeing her overcome that weakness and kick butt was always really inspiring to me.